Present day engine components must be manufactured more simply at significantly reduced costs while achieving superior results in order for engine manufacturers to remain competitive. Unfortunately, exhaust port liners that have produced superior heat insulation capabilities have become more complicated and costly or have incurred increased associated costs for utilizing the invention.
Some exhaust port liners appear to be manufactured more simply, but, assembly requirements have become more complicated to accommodate the new design. Typically, with this design, the cylinder head is machined to include a counterbore for seating the exhaust port liner thereby increasing overall costs of the design.
The goal of one exhaust port liner disclosed in U.S. Pat. No. 4,096,690 by James J. Florek on Jun. 27, 1978 was to provide a heat resistant liner for improving emissions. The liner allows secondary air to enter its interior through apertures partially punched out of the liner body. The emission content, and particularly the hydrocarbon content of the exhaust gases is reduced by secondary chemical conversion within the confines of the exhaust passage of the liner and by appropriate control of the influx of secondary air preferably during the exhaust cycle. The exhaust port liner has an annular flange mounted against a surface which is the sole engagement between the cast cylinder head and the liner. It appears that the flange is used as a seal between the cylinder head and the exhaust manifold. The use of the flange as an exhaust seal requires precise machining of the flange and the cylinder head in order to maintain a desirable surface finish for proper sealing. The precise machining increases the costs associated with the exhaust port liner design. Additionally, the flange must carry all of the clamping load between the cylinder head and the exhaust manifold which could lead to premature failure of the seal damaging the effectiveness of the exhaust port liner.
The present invention is directed to overcoming the problems as set forth above.